German orbital launch vehicle. The EBH (Engel - Bödewaldt - Hanischlaunch) vehicle was a 1949 manned design which would had a gross launch mass of 220 tonnes and delivered a payload of 3 tonnes to a 557-kilometre orbit

Six steps to orbit
A blueprint for a launch vehicle from the forties.
by Juhani Westman

In the late forties almost every theoretician in space flight worth his salt was busy sketching satellite stations in orbit around the Earth and the means of launching them. A range of uses was foreseen, most of which were realized by the sixties with unmanned satellites. At the time it was, however, considered, that they should have to be manned, which meant rather sizable constructions, way beyond the lifting capacity of any conceivable single launch vehicle.

It was clearly seen that the creation of a launch vehicle would be the first order of business, as Rolf Engel, Uwe T Bödewaldt and Kurt Hanisch put it in 1948:

At the present stage of technology...it would be great fun, but without merit, to sketch up the furnishing, or the sleeping or workroom arrangements. What is needed is an exposition of the physical and technical needs and especially the economical capabilities needed to establish such a station.

Thus all the technical discussions started with plans for multistage launch vehicles capable of attaining orbit around the Earth.

Some different schools of thought can be discerned. Wernher von Braun, at the time already in the US, presented his monstrous three-stage "rocket-ship" in "Das Marsprojekt" 1948, at that time in a very stubby form which for aesthetic reasons was slimmed down for the well known Collier' s article series on space flight some years later. The von Braun launcher was rather conventional, three stages in tandem, but it tipped the scale at 6300 metric tonnes, The payload to an orbit with a period of 2 hours was to be some 33 tonnes, plus a cabin for some 10 to 12 people, explicitly "men". Much later, in 1955 -56, von Braun had to re-sketch his launcher for the Disney company, for copyright reasons. He then used the opportunity to downsize it to a gross launch weight of 1280 tonnes with a payload of some 10 tonnes.

The British, RA Smith, H Ross and the trio Gatland, Kuenesh-Dixon, among others, looked to somewhat smaller payloads, and to bring the gross weight of the vehicles down they invented a system of tank staging called "Expendable Construction". Nevertheless their three-stage – more correctly three-stage with four expendable bays in stage 2 - launcher had a gross weight of some 510 tonnes with a 5 tonne payload to a 500-mile i.e. some 800 kilometres orbit.

The smallest of them all.

The smallest launcher was presented in 1949, by the abovementioned German trio Engel, Bödewaldt and Hanisch, who all three during those years were Research Engineers in the French organisation O.N.E.R.A. They wrote up their plans in the Magazine "Weltraumfahrt" of the German post-war organisation "Gesellschaft fuer Weltraumforschung" (Society for Space Research) and it was published under the name "Die Aussenstation", later included in a book by Heinz Gartmann: "Raumfahrtforschung", Oldenburg, Muenchen 1952. Their rocket – the EBH launch vehicle – would have a gross launch weight of some 220 metric tonnes for a payload of 3 metric tonnes to a 557-kilometre orbit, with a period of 1.6 hours, giving 15 orbits per diem. They also calculated the launch weights for a second orbit of two hours period, 12 orbits per diem – interesting enough getting an orbital height of 1669 kilometres against von Braun's 1730 kilometres for the same period.

The insistence on even numbers of orbits around the Earth per diem was predicated on an assumed need for orbit tracking, and for scheduling of the multiple flights to build and to service the space station.

Engel, Bödewaldt and Hanisch did a thorough study on the ascent to orbit. The launch should be vertical, followed by a free trajectory leading up to heights with rarefied air. During the free ascent the rocket should be tilted over towards the east to take advantage of the rotation of the Earth. A more or less horizontal acceleration period would follow, so as not to carry excess amounts of propellants against the gravitation. After attaining circular orbit in an altitude of some 100 kilometres there would follow a short free flight period to be used for small corrections. From this very low parking orbit a short thrust period would raise the apogee to the final altitude, 557 or 1669 kilometres, where a kick manoeuvre would circularise the orbit. Launch was to take place in Woomera in Australia into an orbit with inclination 45 degrees to the equator.

The three authors also studied the optimum number of stages for a satellite launcher using the attainable technology of the day, and came up with an optimum stage number of six.

Adding stages may lower the launch weight substantially. With the rather heavy values for structure mass fraction the authors were calculating with, i.e. Mstr/Mprop= 0,14 for the booster stage and 0,1 for stages 2 and upwards, and given the specific impulse EBH were using, you end up with the following GLOW for a kick stage (originally the sixth stage) mass of 5 tonnes:

Reduction of Gross Lift-Off Mass with added number of stages was calculated as follows:

2 stages + kick stage = 474 tonnes

3 stages + kick stage = 287 tonnes

4 stages + kick stage = 235 tonnes

5 stages + kick stage (EBH) = 220 tonnes

6 stages + kick stage = 216 tonnes

As can be seen the diminishing return sets in already when going from 3 stages to 4 but apparently Engel, Bödewaldt and Hainish felt that the added complexity with five ascent stages and one orbital manoeuvring stage wouldn't prove insurmountable.

Stages

All stages would be using liquid oxygen as oxidant and alcohol as fuel – like the A4 (V2). Calculations show that the given specific impulses in stages 2 to 6 are on the high side but not excessively so. Stage 1 would have a chamber pressure of 50 bar expanded to sea level ambient. In stages 2 and 3 the chamber pressure would be 36 bar, expanded to 0,2 bar. The fuel would be methyl alcohol diluted to 75 %. In the upper stages the methyl alcohol would be undiluted i.e. 92...96 %. The chamber pressure would be lower, only 25 car, in those days high enough as the A4-motor had a Pc of 15 bar. Construction materials would be steel for the engine, duraluminium and aluminium for tanks and hull. The construction would be the same as for the A4, with stringers and longerons stiffening the more or less non-load- carrying skin.

Both the booster stage and the kick stage were to be manned. The pilot in the booster stage would have a hair-raising flight. Sitting in a cylindrical cabin, 2 meters in diameter and 1,8 meter tall, with a plexiglass cupola protruding in the nozzle of the second stage. He would ride the thrusting booster stage for 35 seconds, he then would have 48 seconds to turn it away and "get the hell out from under" before the second stage would commence firing. For landing he would have a set of steering thrusters to stabilize his horribly unstable vehicle, and a propellant reserve giving him some 300 meters per second manoeuvring leeway for a soft landing somewhere in the Australian Outback a couple tens of miles from the launch pad.

To get into his cabin he would have to climb through a passageway alongside the booster thrust chamber-nozzle assembly, inside the annular four-section fuel-and-oxidizer tanks.

Stages 2 to 5 would be unmanned, all built to the same format with annular tanks and the engine assembly in the middle. Stages 4 to 6 would have spherical tanks and the layout would not be unlike that of the EPS Upper Stage of Ariane-5.

Upstairs in the sixth stage – the kick-stage which would attain the final 557 kilometre orbit – would be a cabin for two pilots and a payload, consisting of 1 tonne propellants and 1,5 tonnes dry load. Here we discern a fudge factor: the authors assume that 0,5 tonnes of the stage itself would be usable for the space station construction, thus adding up to the advertised 3 tonne total payload.

In 1948 nothing much was known of the re-entry problem, and the authors side step the whole issue, declaring that the pilots "would be returning in a special vehicle, built on the lines of the projected Sänger Antipodal Glider".

Cost analysis.

There was also a cost analysis. Taking the dry mass, and estimating the time and cost of producing it from the known amount of time needed to produce A4 (V2) missiles, and the then current aerospace production costs, the authors arrived at a production cost of USD 73 000, (1948!!) for the A4 and USD 702 000 for the EBH launch vehicle, in both cases including propellants. The costs of reading the launch vehicle for launch, and other operating costs were not - could not be - estimated. With 20-20 hindsight one could foresee quite a hefty cost addition for launch and flight operations, as each of the six stages would have to be checked out as independent vehicles before being integrated.

In its day, the EBH vehicle was hailed as the most realistic forecast to date, as the size was not too daunting, the propellants were well known and the construction and specific impulse seemed achievable. Today this plan is all but forgotten, when the much more futuristic monster rocket by von Braun, with it's then exotic propellants, nitric acid and hydrazine, crops up in most recapitulations of the prehistoric eras of astronautics.

The number of stages seems excessive today, but it is well to remember that a four-stage vehicle, the Jupiter-C/Juno I, launched the first US satellite. The larger Juno-II was likewise a four-stage vehicle. Also, the principle of a launch trajectory with a free-flying phase with tilting between lofting to altitude and acceleration to orbit, was adhered to in both the Vanguard and the Juno vehicles.

Looking at the numbers, one could imagine a vehicle with solid propellants for the stages giving an equal performance; of course the visible layout of the vehicle would be quite different from the flying artillery shell imagined by Engel, Boedewald and Hanisch.